Eli5: How come when I’m stopped in a car and I let go of the brakes, it moves forward without touching the accelerator?

Question

Eli5: How come when I’m stopped in a car and I let go of the brakes, it moves forward without touching the accelerator?

In: Engineering

Answer 1

Two things:

1. I don’t know the exact details of why this happens, but if a car’s engine turns any slower than about 1,000 RPM, it will stall. So, the car is designed so that the engine is always turning at at least 1,000 RPM even when you’re not touching the accelerator.
2. A car with an “automatic” transmissions always has its engine powering its wheels as long as you’re not braking. So, that leisurely little 1,000 RPM makes the car move without any accelerator input.